Field of the Invention
The present invention relates to 3D printing, in particular to a method of 3D printing based on a combination of extrusion and photopolymerization of a polymer paste. More specifically, the invention relates to a method of 3D printing with use of a hand-held 3D printing device and with photopolymerization of the extruded thread.
Description of Prior Art
Three-dimensional (3D) printing is the extrusion of a curable substance into a three-dimensional space to create a physical object, e.g., on the basis of a virtual three-dimensional model.
Three-dimensional printing technology originated in the mid-twentieth century, the same time at which the first 3D printers appeared. The price of these devices ranged from a few dozen to several hundred thousand dollars.
Presently, 3D printing processes are divided into the following basic categories:
1. Extrusion of material;
2. Photopolymerization;
3. Printing by sintering and melting of a material;
4. Printing objects by lamination of layers;
5. 3D printing by the Mcor technique (Mcor Technologies, Ireland and US); and
6. Contour manufacturing.
In terms of the material used for printing, 3D printing processes comprise the following three main groups:
1. Plastics, casting wax (this category also includes other materials suitable for creating 3D models by casting or melting);
2. Powders (this category includes all materials in powder form as well as powdered metals and metal alloys suitable for forming 3D objects); and
3. Photopolymers (including liquid photopolymers and resins).
All three classifications are closely related and require certain conditions for printing, i.e., the use of an appropriate technology. For example, printing with the materials listed in the first group requires the use of a special printing head with a heating element to melt the material and a mechanism for feeding the material to the nozzle. The second group requires the use of a special mechanism for changing or leveling the powder, as well as for thermally or optically affecting the material for curing. Material of the third group requires provision of a special feeder for photopolymer material as well as provision of a special source of light radiation.
Printers currently used for 3D printing are based on the extrusion of materials according to the principles of FDM (Fused Deposition Modeling) and DOD (Drop On Demand).
FDM is an additive manufacturing technology commonly used for modeling, prototyping, and production applications. FDM works on an “additive” principle by laying down material in layers; a plastic filament or metal wire is unwound from a coil and supplies the material to produce a part. The technology was developed by S. Scott Crump in the late 1980s and was commercialized in 1990. The term fused deposition modeling and its abbreviation FDM are trademarks of Stratasys.
DOD technology is a layered deposition of molten material droplets and the subsequent milling of each layer. Unlike the technology FDM, material melts before entering the printing head. The milling head cools the material and grinds the surface.
Both DOD and FDM processes use supports that are printed to form complex objects. The supports can be printed from the basic material or from a special material. To obtain final objects, the supports are removed. The photopolymerization technique uses a 3D printer based on SLA (stereolithography), MJM (Multijet Modeling), DLP (Digital Light Processing), and PolyJet (photopolymer materials sprayed onto a build tray in ultrathin layers until the object is completed).
Although 3D printing pens are relatively new products in the industry, some hand-held devices for 3D printing are known in the art.
For example, Chinese Patent Application Publication CN103707511 (A) of Apr. 9, 2014 (inventor: Bao Huhe) describes a 3D printing pen that comprises a shell with an outlet nozzle on one end and a material-feeding opening on the other end. The material is fed through a feeding tube to the nozzle via an adjustable electric heater and is extruded through the orifice of the nozzle. In such a device the material can be supplied in the form of a viscous liquid (e.g., an oligomer) or in the form of solid matter. In the first case, the extruded material is cured when exiting the nozzle. In the second case the solid material melts by preheating and then returns to a pasty or solid state with the lapse of time after exiting the nozzle.
Chinese Utility Patent CN203449607 (U) of Feb. 26, 2014 (inventors: Haixiong, et al) describes a 3D printing pen that comprises a housing that contains a heating coil for heating a material which is fed through the feeding tube arranged along the housing and then extruded through the nozzle located on the side of the housing opposite the material inlet opening. The heating coil is located near the nozzle at the output end of the feeding tube. The device is provided with a sensor and a control circuit. The heating temperature is shown on a small display provided on the side of the housing.
Chinese Utility model CN203371791 (U) of Jan. 1, 2014 (inventor: Wenliang) discloses a 3D pen that comprises a printing pen body consisting of a shell and an internal hollow body, wherein the front end of the shell comprises a discharging nozzle and the rear end of the shell comprises a feeding port. The feeding port and the discharging nozzle are connected with a feeding channel arranged in the hollow body. By connecting the feeding pipe at the tail part with the heating core at the front part, the feeding channel is formed. One end of the feeding pipe, which is close to the feeding port, is provided with a driving device in a linking manner. The driving device consists of a feeding control motor and a guiding wheel, which are linked. The space formed by the heating core and the shell is filled with insulated silica gel. A ventilating port is formed between the insulated silica gel and the shell in a blocking manner. The inner part of the hollow body also comprises a cooling fan, which communicates with the ventilating port. The 3D printing pen disclosed by the utility model has the advantage of a polymer material such as ABS (Acrylonitrile Butadiene Styrene), which is preheated or cooled to a certain temperature and is continuously discharged. The temperature of the material is constantly adjusted and maintained at a required level.
Chinese Utility Patent CN203357906 of Dec. 25, 2013 (inventors: Feizuo, et al) discloses a 3D printing pen that comprises a housing, an outlet head with a nozzle, a heating cavity, a drive motor, a material-feeding pipe, and a control panel with control buttons wherein the outlet head, the heating cavity, the drive motor, the material-feeding pipe, the control panel, and the control buttons are arranged in the housing. The outlet head is located at the front end of the housing. The heating cavity is arranged at the rear end of the outlet head. The control panel is provided with a control module, a power supply module, a heating module, and a motor module.
Chinese Patent Application Publication CN103341975 (A) of Oct. 9, 2013 (inventors: Feizuo, et al) discloses a 3D printing pen which in its structure and function is similar to one described in one of the aforementioned specific publications.
It can be seen that all methods of 3D printing with the use of a known 3D printing hand-held device such as, e.g., a 3D printing pen, are based on a thermal process for softening and melting of the material to be extruded through the nozzle of the 3D printing pen. In case of a polymer, heating provides thermal curing, which is achieved by arranging a heater, such as an electric heater, inside the housing of the device.